Interactive systems for allowing collaborative document markup are known. For example, networked computer terminals can be used to share information in real time between participants in mutually disparate geographical locations by way of conventional terminal display means. By making use of the Internet, Web pages displayed on the terminal screens can be used in carrying out a collaborative activity, such as collaborative document markup. Each participant has access to a computer means that is networked with the computer of the other participants. Each participant's screen acts as a ‘virtual document’, allowing the participant to add a markup to a working document, which document is then ‘delivered’ to the other participants for display on their respective screens, and for subsequent printing if desired.